1. Field of the Invention
The present invention relates to a flying magnetic head for rigid disk applications, and more particularly, to a composite flying magnetic head whose head core comprises a laminated thin film core.
2. Description of the Related Art
Generally, the flying magnetic head for rigid disk applications is composed of a slider and a head core, and is attached to a suspension system for maintaining the head slider in position on or above a magnetic disk surface.
Conventional flying magnetic heads include (1) the monolithic type whose slider is manufactured by forming a gap in part of a ferrite and then by cutting and polishing that ferrite into a predetermined form, and (2) the ferrite composite type manufactured by bonding a head core made of ferrite to a slider made of a non-magnetic material such as a ceramic using glass. Recently, the so-called MIG (metal-in-gap) composite flying magnetic head in which magnetic thin films are deposited onto either side or both sides of a gap formed in a ferrite head core has been drawing attention. These magnetic thin films are made of Fe-Si-Al alloy (Sendust) or an amorphous magnetic material both of which have a high saturation magnetic flux density and a magnetic permeability exhibiting excellent high-frequency characteristics, and which thus assure high density recording. In the ferrite and MIG composite flying magnetic heads, a head core 1 is fitted into and bonded by means of a bonding glass 4 to a slot 3 which has a predetermined form and which is formed in a ceramic slider 2 obtained by cutting and polishing a monolithic ceramic, as shown in FIG. 5.
Also, a thin layer laminated, composite flying magnetic head which employs a laminated thin film core as a head core has been employed in a VCR system. This laminated thin film core is obtained by laminating a magnetic Fe-Si-Al (Sendust) alloy film or an amorphous alloy film on a non-magnetic substrate. Such a composite head with a laminated thin film core is disclosed in, for example, Japanese Patent Application Public Disclosure No. 18617/1987. In this flying magnetic head, a head core 1 is fitted into and bonded by a bonding glass to a slot 3 which has a predetermined form and which is formed in a ceramic slider 2 formed by cutting and polishing a monolithic ceramic, as shown in FIG. 6(A) to FIG. 6(C) of the present application.
The present inventors found in the process of developing the composite flying magnetic head that an unbalanced wear occurs between the slider and the head core, that the surface of the bonding glass is made rough during the CSS (contact-start-stop) operation, and that dust contaminating particles) attaches to the rough surface of the bonding glass, lowering the ability with which the magnetic head withstands the CSS operation.
That is, in the ferrite and MIG composite flying magnetic heads, the slider and the head core are made of different materials, and the portion of the head core located near the gap is made thinner, as shown in FIG. 5, in order to achieve reduction in the track width and the surface area of the bonding glass layer is thus increased. In consequence, the ability with which the magnetic head withstands the CSS operation is reduced. Furthermore, in the conventional composite flying head with laminated thin film core, no consideration is given to the surface area of the bonding glass.
The present inventors made intensive studies to solve this drawback of the conventional magnetic heads and found that it can be solved in a composite flying magnetic head which employs a laminated thin film core as a head core when the housing (or slider) and non-magnetic substrate of the head core are made of the same material, when the coefficient of thermal expansion of the material of the substrate of the head core is substantially the same as that of the magnetic thin film of the head core, and when the thickness of the bonding glass layer which bonds the head core to the slider is reduced to a very small value.
That is, when the slider and the substrate of the head core (head chip) are made of the same material, an unbalanced wear between the slider and head core is eliminated. When the coefficient of thermal expansion of the slider is substantially the same as that of the substrate of the head core, the stress applied to the bonding glass layer which bonded the head core to the slider, can be reduced greatly, and hence, deterioration of the glass layer after bonding can be prevented resulting in an increase of reliability thereof.
Further, though in the conventional ferrite head type and MIG composite flying magnetic heads, as shown in FIG. 7, only a front gap portion (FG) is shaped to make a track width (W) narrower, the thickness (T) of a rear gap portion (RG) should be between about 150 .mu.m to about 200 .mu.m maintain a mechanical strength of the head core. For example, when the track width (W) is less than 20 .mu.m the thickness of the glass layer to bond the head core 1 to the slider requires a thickness of about 100 .mu.m to about 200 .mu.m.
On the other hand, since in the head core of the present invention the track width can be determined by the thickness of the magnetic alloy layer both sides of which are reinforced by a ceramic material, the thickness of the glass layer to bond the head core to the slider can be reduced greatly.
Thus, the present invention can realize a composite head as a whole without deterioration of the glass used for the glass layer, with maintaining high reliability and by making the thickness of the bonding glass layer less than 20 .mu.m, further less than 10 .mu.m.
Further, according to the present invention the thickness of the bonding glass layer can be reduced greatly, thereby reducing the rough surface area of the mechanically weak glass layer and, hence, the amount of dust (contaminating particles) adhered to that surface. This results in the improvement in the ability with which the magnetic head withstands the CSS operation.
When the coefficient of thermal expansion of the substrate of the head core is substantially the same as that of the magnetic thin film of the head core, stress applied to the magnetic thin film can be reduced, thereby eliminating deterioration in the magnetic characteristics of the head.
The present invention is based on the above-described novel knowledges.